The state of the art in seedling transplant propagation involves the use of a large tray having a rectangular array of individual cells for containing a transplant medium into which individual seeds or root cuttings are placed and grown under greenhouse conditions. Currently this large tray most often comprises a molded Styrofoam plastic tray such as is illustrated in FIGS. 1 and 2 of the drawings and is sold under the trade mark "Speedling." Other have proposed many different forms of transplant propagation trays such as, for example, the ones taught and illustrated in U.S. Pat. Nos. 4,769,946, 4,658,542, 4,495,725, 4,242,834, and 3,386,608.
In some countries, such as the Netherlands, the technology of transplant propagation has become quite sophisticated and mechanized. Apparatus has been constructed with various machine stages for dropping soil into the cells in the tray, brushing off excess soil, forming an indentation for the seed hole, dropping seeds into each seed hole in each cell, spreading vermiculite or other mulching over the dirt, and watering the plug. For example, U.S. Pat. No. 4,221,175 illustrates a machine for dropping seeds into individual cells of a multicell tray.
Several disadvantages are involved in the use of the Speedling type of instant propagation tray and many of the other types of tray that have been proposed. The trays typically dont't last more than several growing seasons over a two or three year period. Toward the end of their useful life, the Speedling trays tend to deteriorate with the surfaces of the cell walls getting rougher and making it more difficult to remove the transplant plug from the tray. The trays are bulky and thus difficult to and costly to ship from the nursery to the planting location. Cleaning of the trays after use can be difficult since the side walls of the main individual cells are not readily accessible to brushing. Storage of the bulky trays when not in use consumes a lot of space. Disposal of the Styrofoam plastic trays may create environmental problems.